GE DS3800DXRA

Technical Specifications

• Product Type: Digital Expansion Relay & Alarm Board

• Part Number: DS3800DXRA

• Manufacturer: General Electric (GE)

• System Compatibility: GE Speedtronic Mark IV Turbine Control Systems

• Output Channels: 16 digital outputs (Form C – SPDT relays)

• Contact Rating: 5A @ 250VAC or 5A @ 30VDC (resistive); 2A @ 250VAC (inductive)

• Surge Suppression: Built-in RC snubbers and flyback diodes per channel

• Indicators: Front-panel LEDs per channel

• Isolation: 1500Vrms opto-isolation between logic and field contacts

• Expansion Interface: Backplane connection to Mark IV processor; no direct processor slot required (slave mode)

• Temperature Range: 0°C to +60°C

• MTBF: > 150,000 hours (MIL-HDBK-217F)

Key Features & Advantages

• Expansion Capacity: The GE DS3800DXRA adds 16 relay outputs to the system, allowing more alarms and control signals without occupying a processor slot.

• Form C Contacts: Each channel provides both NO and NC contacts, offering flexibility for energize-to-trip and de-energize-to-trip configurations.

• Slave Operation: The GE DS3800DXRA operates as a slave board, receiving commands from the main processor via the backplane, reducing processor overhead.

• Built-In Surge Suppression: Includes flyback diodes and RC snubbers for inductive loads, protecting contacts and logic circuits.

• Diagnostic LEDs: Front-panel LEDs indicate output status per channel.

• Cost-Effective Expansion: Provides additional I/O without requiring a full processor upgrade or additional rack.

Typical Application Cases

• Expanded Alarm Annunciation: The GE DS3800DXRA adds extra alarm channels for detailed turbine status reporting to annunciator panels.

• Additional Control Outputs: Provides extra outputs for auxiliary equipment such as cooling fans, heaters, and lighting.

• Remote Signaling: Sends additional status signals to plant DCS or SCADA systems.

• Interlock Logic: Provides extra relay contacts for safety interlocks and permissives.

• Retrofit Projects: Used when upgrading older Mark IV systems that require more I/O than originally configured.

Competitive Comparison

The GE DS3800DXRA is a cost-effective expansion solution for Mark IV systems requiring additional relay outputs. Modern expansion modules offer digital communication but require fieldbus integration.

Selection Guidelines & Precautions

1. Channel Count Verification: Confirm the number of additional outputs required. The GE DS3800DXRA provides 16 channels; multiple boards can be installed if more are needed.

2. Processor Compatibility: Ensure the Mark IV processor supports expansion boards. Most standard configurations do, but verify firmware compatibility.

3. Contact Current Verification: Confirm load current does not exceed 5A resistive or 2A inductive. For larger loads, use external interposing relays.

4. Wiring: Use shielded cables for field wiring. Ground shield at the GE DS3800DXRA end only.

5. Address Configuration: The GE DS3800DXRA requires backplane address configuration. Consult the Mark IV manual for proper jumper settings to avoid address conflicts.

6. ESD Handling: Use ESD-safe practices.

7. Sourcing: Obsolete. Request functional test report including:

   • All 16 channels tested under rated load

   • Contact resistance measurement (< 0.1Ω new, < 0.5Ω refurbished)

   • Surge suppression verification

   • Address configuration validation

8. Spare Strategy: Keep one spare GE DS3800DXRA on-site if additional relay outputs are critical for alarm annunciation or control functions.